Question

A wavelength of $450$ $nm$ corresponds to :
$(1$ $nm$ = ${10}^{-9}m)$

• A. Frequency$\left(\nu \right)$ $=6.6\times {10}^{14}Hz$
• B. Wave number$\left(\tilde{\nu }\right)$ $=2.2\times {10}^6{m}^{-1}$
• C. None of the above
• D. Both (a) and (b)

Answer 1

The correct option is D Both (a) and (b)

Frequency is given by:
$\nu$ = $\frac{c}{\lambda }$
where $c=$ speed of light
and $\lambda =$ wavelength

We know that,
$c=$ $3\times {10}^{8}m/s$
$\lambda =$ $450$ $nm$ $=4.5\times {10}^{-7}m$
Substituting the values, we get
$\nu$ = $\frac{3\times {10}^8}{4.5\times {10}^{-7}}$$=6.6\times {10}^{14}Hz$

Wave number is given by:
$\tilde{\nu }=\frac{1}{\lambda }$
$=2.2\times {10}^6{m}^{-1}$